[2019 CFORCE 400S]

Hello group.  I own a 2019 CFORCE 400S  I tried to mount a Kolpin Stronghold® Gun Boot® L w/ Autolatch Mount to the rear rack...however there is not enough tubing to mount it properly (three contact points).  Has anyone done this and knows a trick...or know of a Kolpin bracket that works with this bike...or any other brand?

Thanks in advance

Rob